This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This subproject (phase 5) is the most challenging one, poised to further develop the multi-sample probe in order to enable high-speed sample switching, which we refer to as processing them in a "round-robin" fashion. For this development we have conceptual solutions for both standard (50-60K) and low (8-20K) temperature ranges. The second temperature range is also attractive for integrating the probe with a cryogenic receiver. In the case of successful implementation of such type of a probe we shall integrate it with a cryogenic receiver. The development of the multi-sample probe is the most challenging aspect of the project requiring substantial research, including but not limited to the development of a "set-on" or else multi-channel microwave receiver, control and DSP software, cryogenic receiver protector, and other key parts. The technology involved encompasses considerable high-precision machining, hard material grinding and polishing to high accuracy, fabricating microwave assemblies and vacuum parts, and electronic circuits. The successful completion requires access to suitable engineering resources, which we have in part at ACERT (in particular Boris Naumov), and we will outsource to U.S. companies, as needed. Overall, the project though technically very challenging, entails achievable goals at reasonable cost.